Enable lazy/sparse allocation of generation symlinks: avoid creating

new generations if a generation already exists.

Alternatively or additionally I propose a mode where only the *last* generation will be sparse.

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/user-envs.sh b/tests/user-envs.sh
index c9eed5a663..ad15ddc3e4 100644
--- a/tests/user-envs.sh
+++ b/tests/user-envs.sh
@@ -99,6 +99,15 @@ if nix-env -q '*' | grep -q bar; then false; fi
 nix-env --list-generations
 test "$(nix-env --list-generations | wc -l)" -eq 7
 
+# Doing the same operation twice should result in the same generation, not an
+# additional one. At this point we just brought back foo. Installing it again
+# should not create a new generation.
+nix-env -i foo
+
+# Count generations.
+nix-env --list-generations
+test "$(nix-env --list-generations | wc -l)" -eq 7
+
 # Switch to a specified generation.
 nix-env --switch-generation 7
 [ "$(nix-store -q --resolve $profiles/test)" = "$oldGen" ]